A massive heart attack!
Why people depend on artificial energy is beyond me. I agree with dyna mo, eating clean is the best form of energy. Eat, train, sleep and you'll be fine. The only caffeine I get is my small cup of green tea every morning with honey (or agave nectar). I wake up at 5am, go to bed at midnight, and have enough energy to train MMA for 3 hours a night and 1 hour of strength training/cardio in the morning - 6 days a week.
There's these things called dependency and crashing. Once you quit putting that shit into your body, which can't be healthy, then you're going to crash and your body won't know how to synthesize/utilize what it needs for natural energy; carbs, fats, etc.
Eat clean, train hard, live long.
